When I'm trying to hack, empty page is opening. How do I hack so?

UPD: fixed, ty codeforces

Why there is a new icon? What it means? Why MikeMirzayanov didn't wrote about it (or I just didnt note)? And what happened to the old icon?

I am finally pupil! Yeehaw!!!

Why system testing on Div2 rounds is fast, while system testing on Div.3 and Div.4 are so long? Is it Div.2 rounds specific or the reason is the number of submissions (on Div2 it's probably smaller than on Div3-4 ones)?